No systems or algorithms in this world are perfect. And yes, it’s the same for us too.
While we have great accuracy in identifying an email address as CLEAN or DIRTY, but there is always a chance when we are unable to do so. So, instead of blindly categorizing such email addresses as Clean or Dirty, we share transparency with you and categorize these addresses as UNKNOWN.
As, we are unable to positively categorize these addresses into any bucket, so now it’s up to you to decide whether you really want to reach out on such Unknown email addresses.
Definitely, you should never send email campaigns on a DIRTY email list, but UNKNOWN email list is a grey area, and hence can be targeted with utmost caution.